1. Field of Invention
This invention relates to security systems and more specifically security systems that can detect concealed weapons, explosives or other types of contraband objects that may be carried by a person on, under, or within his clothing.
2. Discussion of Related Art
Because of the threat of terrorism, it is desirable to have a way to detect explosives, weapons or other contrabands concealed by individuals on their persons. The approaches traditionally used to inspect luggage or other containers for contraband are generally not suitable for detecting contraband concealed by individuals on their persons. Most known inspection techniques employ ionizing radiation to form images of items under inspection. Human operators or computer systems programmed with image analysis algorithms can study these images to detect contraband objects concealed within containers.
Because of health risks imposed by ionizing radiation, similar systems may not be used to detect contraband items concealed by people, for example, beneath their clothing. Even imaging systems that employ non-ionizing radiation are not desirable. Many people object to being irradiated, even if the level or frequency of the radiation is not associated with any known health risk.
It has been proposed to use millimeter waves (“mm waves”) to image people for contraband detection. However, mm wave cameras can produce images of people in which their clothes are not visible. Such a system may also be objectionable to the people who would be inspected by it.
It would be desirable to have an improved contraband detection system.